Battery assemblies formed by connecting a plurality of battery cells in series, wherein a storage element (physical battery) such as a lithium ion battery, a nickel hydrogen battery, another secondary battery, or a capacitor is used as the battery cell, have grown in importance as power supplies from which high output is obtained, and are used as power supplies installed in vehicles or power supplies for personal computers and portable terminals. A battery assembly formed by connecting in series a plurality of battery cells constituted by lithium ion batteries, which are lightweight and achieve high energy density, can be used particularly favorably as a high output power supply installed in a vehicle.
Incidentally, a cylindrical battery cell may be used as the battery cell in this type of battery assembly. When a cylindrical battery cell is used in the battery assembly, a battery structure in which an external terminal (typically a screw structure) is fastened to one or both ends of the cylindrical battery cell (a cylindrical battery cell case) is known as a representative basic structure thereof. A connecting member (a bus bar, for example) for connecting the battery cells and a fixing member (a so-called holder) for fixing the battery cells are respectively fastened to the external terminal (typically a screw structure). For example, Patent Document 1 discloses an example of a cylindrical battery cell for installation in a vehicle. Further, Patent Document 2 discloses an example of a battery assembly including a plurality of cylindrical battery cells.
When this type of cylindrical battery cell is incorporated into a battery assembly, a rotation stopping mechanism must be provided to prevent fastening torque generated when the external terminal (typically a terminal of a screw structure) is fastened from causing a battery main body (a main body part of the cylindrical battery cell) to rotate together with the external terminal. Conventionally, a fixing mechanism that uses a jig to prevent the battery from rotating is employed as this type of rotation stopping mechanism. Alternatively, a method of providing the battery itself with a rotation stopping function may be employed. More specifically, a mechanism that provides the external terminal and accessories thereof with a rotation stopping function is employed.
Patent Document 1: Japanese Unexamined Patent Application Publication 2005-78805
Patent Document 2: Japanese Unexamined Patent Application Publication 2000-173676
However, with the former rotation stopping mechanism (a fixing mechanism that uses a jig to prevent the battery from rotating), a separate dedicated jig must be designed and manufactured, and moreover, the number of operating steps involved in assembling the battery assembly increases, possibly leading to an increase in cost. Furthermore, space for attaching the jig must be secured in the battery assembly, which may inhibit reductions in the size of the battery assembly. Meanwhile, with the latter rotation stopping mechanism (a mechanism for providing the external terminal and the accessories thereof with a rotation stopping function), increases occur in the number of components and the amount of component processing in direct relation to the process for providing the external terminal and the accessories thereof with a rotation stopping function, which may again lead to an increase in cost. Hence, there is room for improvement in a conventional rotation stopping mechanism in terms of the number of operating steps and the manufacturing cost involved in assembling a battery assembly.